ParameterExpression

qiskit.circuit.ParameterExpression(symbol_map, expr)

Bases: object (opens in a new tab)

ParameterExpression class to enable creating expressions of Parameters.

Create a new ParameterExpression.

Not intended to be called directly, but to be instantiated via operations on other Parameter or ParameterExpression objects.

Parameters

• symbol_map (Dict[Parameter, [ParameterExpression, float (opens in a new tab), or int (opens in a new tab)]]) – Mapping of Parameter instances to the sympy.Symbol serving as their placeholder in expr.
• expr (sympy.Expr) – Expression of sympy.Symbol s.

---

Attributes

parameters

Returns a set of the unbound Parameters in the expression.

---

Methods

abs

abs()

Absolute of a ParameterExpression

arccos

arccos()

Arccos of a ParameterExpression

arcsin

arcsin()

Arcsin of a ParameterExpression

arctan

arctan()

Arctan of a ParameterExpression

assign

assign(parameter, value)

Assign one parameter to a value, which can either be numeric or another parameter expression.

Parameters

• parameter (Parameter) – A parameter in this expression whose value will be updated.
• value (ParameterExpression |float (opens in a new tab)) – The new value to bind to.

Returns

A new expression parameterized by any parameters which were not bound by assignment.

Return type

ParameterExpression

bind

bind(parameter_values, allow_unknown_parameters=False)

Binds the provided set of parameters to their corresponding values.

Parameters

• parameter_values (dict (opens in a new tab)) – Mapping of Parameter instances to the numeric value to which they will be bound.
• allow_unknown_parameters (bool (opens in a new tab)) – If False, raises an error if parameter_values contains Parameters in the keys outside those present in the expression. If True, any such parameters are simply ignored.

Raises

• CircuitError –

  • If parameter_values contains Parameters outside those in self. - If a non-numeric value is passed in parameter_values.

• ZeroDivisionError (opens in a new tab) –

  • If binding the provided values requires division by zero.

Returns

A new expression parameterized by any parameters which were not bound by parameter_values.

Return type

ParameterExpression

conjugate

conjugate()

Return the conjugate.

Return type

ParameterExpression

cos

cos()

Cosine of a ParameterExpression

exp

exp()

Exponential of a ParameterExpression

gradient

gradient(param)

Get the derivative of a parameter expression w.r.t. a specified parameter expression.

Parameters

param (Parameter) – Parameter w.r.t. which we want to take the derivative

Returns

ParameterExpression representing the gradient of param_expr w.r.t. param or complex or float number

Return type

ParameterExpression | complex (opens in a new tab)

is_real

is_real()

Return whether the expression is real

log

log()

Logarithm of a ParameterExpression

sign

sign()

Sign of a ParameterExpression

sin

sin()

Sine of a ParameterExpression

subs

subs(parameter_map, allow_unknown_parameters=False)

Returns a new Expression with replacement Parameters.

Parameters

• parameter_map (dict (opens in a new tab)) – Mapping from Parameters in self to the ParameterExpression instances with which they should be replaced.
• allow_unknown_parameters (bool (opens in a new tab)) – If False, raises an error if parameter_map contains Parameters in the keys outside those present in the expression. If True, any such parameters are simply ignored.

Raises

CircuitError –

• If parameter_map contains Parameters outside those in self. - If the replacement Parameters in parameter_map would result in a name conflict in the generated expression.

Returns

A new expression with the specified parameters replaced.

Return type

ParameterExpression

sympify

sympify()

Return symbolic expression as a raw Sympy or Symengine object.

Symengine is used preferentially; if both are available, the result will always be a symengine object. Symengine is a separate library but has integration with Sympy.

tan

tan()

Tangent of a ParameterExpression